Gurdieff's harmonium improvisations, which often followed the dinners which he held in his Paris apartment during the Occupation and immediate post-war years, to his death in 1949.
NOTE: The recordings are Public Domain in the European Union (as recorded more than 50 years ago), but as far as I understand not so in the US. I am not sure who actually would hold the US copyright though... all very confusing. I have put them under a Public Domain Mark 1.0 as there doesn't seem to be an option for work which varies from jurisdiction to jurisdiction but which is not your own. Would be great to have this option (maybe linking up in some way with the Public Domain Calculators project when it is done?)